Apparatus for testing materials with regard to their tensile strength



July 28, 1942. J ssou 2,290,868 APPARATUS FOR TEsTING MATERIALS WITH REGARD To THEIR TENSILE STRENGTH FiIed Oct. 16, 1939 Patented July 28, 1942 PATENT OFFICE 2,290,868. APPARATUS FOR, TESTING MATERIALS WITH REGARI! STRENGTH TO THEIR TENSILE Johan Helge Eriksson, Finspong, Sweden Application October 16,1939, Serial No. 299,757 In Sweden November 4, 1938 9 Claims.

The present invention relates to apparatus for. testing materialswith regard to their tensile strength.

The main object of the invention is to provide an apparatus of thi type in which the influence of temperature var ations upon the testis eliminated] Other objects will be obvious from the following description of one embodiment of the inventi-c-n, shown in the annexed drawing.

Fig. 1 shows a vertical section of the apparatus according to the invention.

Fig. 2 shows a horizontal section taken on the line IIII in Fig. l.-

Fig. 3 shows a portion of the section according to Fig. 1 on a greater scale.

Fig. 4 is a diagrammatical view of a lever system operating the indicator device.

According to the present invention, in addition to the usual test bar, a second bar of the material to .be tested, is arranged in operative connection with the indicator device in such manner, that it compensates fOr temperature variations.

For obtaining thisresult the tensile test according to the invention is carried out in the following manner: Two equal pieces, such as bars, of the material, which is to be tested, are V arranged in such manner in relation to the indiother, upon the indicator device, which, thus. will I not make any deflection, when the variations of the length of the bars are equal. Then, one of these bars, viz. the test bar, is subjected toa tensile load, and the elongation of the same in relation to the other, non-loaded bar, viz. the comparison or compensating 'bar, is measured.

By locating the two bars in an externally insulated chamber, in which the same temperature exists throughout, the two bars are kept at the same temperature duringthe test. If desired, it

- is possible to keep this chamber heated to any.

high temperature. This is important in view of the fact, that the high temperatures, which nowadays are used in the mechanical engineering and elsewhere, require that the strength of the materials be testedunder the temperatures, to which they are subjected in practice. According to the invention such tests maybe carried'out in a reliable manner by means of a simple apparatus. However, this apparatus may be used also f r normal tensile tests without heating, but

when elimination of variations of the temperature of the surrounding atmosphere is desired.

In Fig. 1 of the drawing the reference numerals I and 2' indicate two equal or substantially equal bars of the material, the tensile strength of which is to be tested. Thetwo bars are. mounted between a lower-holder 3 and an upper holder 4 within a chamber 5, which is surrounded by a heat-proof material 5, for instance a cylinder of heat-proof cast iron, having a bore throughout, which forms the chamber 5. The cast iron cylinder 6 is surrounded, for instance, byan electrical heating element I and is, further, outside the .heating' element, enclosed by an insulation 3, which is enclosed by a sheet-metal covering 9. In the drawing the elements v69-enumerated above constitute an externally cylindrical body, the holders 3 and 4 protruding through the-opposite ends of this body. The lower. holder 3 is connected with a stand III by means of a screwand nut-connection ll, which 'allows acertain adjustment of the holder'3 in its longitudinal direction (on the drawing in the vertical direction). 3 The-upper holder 4 is guided slidably in an opennected with a lever l4, which is mounted at l3 and carries an adjustable weight-load, in the drawing indicated by the arrow P.

The bar I, viz. the test bar, has its lower end screwed into the holder 3 and has its upper end screwed into the holder 4, as shown in Fig. 3,

whereas the bar 2, viz. the compensating bar, has its lower end resting loosely in a recess in the where, however, the clearance of the bar end is excessively designed. Above the bar I the holder 4 has a similar bore l 5. At the top the two bores 40 I 5, I 6 open into a transverse aperture in the holder 4. Each bore contains a quartz bar I8 and [9 respectively, which bears upon'th'e upper end of the corresponding bar I, Land the upper end of which terminates in the aperture ll. The 45 quartz bars serve the purpose of transmitting the variations of the length "of the bars |,-2 to an indicator device, independent of variations of the length of the holder 4. Therefore, they are lodged loosely in the bores l5, IS. The upper ends of the same preferably are provided with metallic ferrules shaped as points.

One end of a lever 20 bears upon the point ofthe bar I8 and one end of a lever 2| bears upon the point of the bar IS. The last-mentioned on lever hasthe otherend bearing upon a stationary holder 3 and has its upper end engaging a vertical bore I6 in the holder 4, as shown in Fig. 3,

prop, in the drawing shown as the point 01 a bar 22,- which has the lower end, also shaped as a point, resting upon a bearing 23 on the stand ID of the apparatus, which bearing preferably is adjustable in the vertical direction. The lever 20 bears, by means of an intermediate fulcrum or edge 24, upon the lever 2| and is connected, at the other end, to an indicator device. This may be of any type, but is, in the drawing, shown as an optical system having a mirror 26 fixed to a roller 21, around which a weight-loaded thread 28 attached to the end 25 of the lever 20, is wound. The dashed lines provided with arrows, indicate an incident and reflected light ray. The lever 20 is held against the point of the quartz bar I8 by means of a spring-pressed pin 29, mounted in the holder 4- above the aperture II.

The lever system described above is of suchconstruction, that equal variations of the length of the two bars I and 2 to not influence the indicator device. The principle of the construction is illustrated in Fig. 4. The reference numerals are the same as in Fig. 1. In addition, the arms of the lever 20 are indicated by Li and L2 and the arms of the lever 2| are indicated by I1 and la. The terminal 25 of the lever20 points directly at a scale. 11 the ratio of L1 to L2 is as, the ratio of ii to Is, a parallel displacement of the operating points of the quartz bars in the vertical direction will not cause any movement of the terminal point 25 of the lever 20. Thus, such variations in the length of the two bars I and 2, which are caused by variations of the temperature, have no eifect on the indicator device, because the two bars always have the same temperature and, thus, are subjected to the same variations of the length when the temperature changes. By means of the heating element I the temperature in the chamber 5 may such construction, that it'multiplies' the deflection of the lever system, for instance 50 times.

- Thus, the final indication constitutes a multiple of the true elongation, which multiple is obtained by the two multiplications, and which indication, in the example referred to, is 1000 times greater than the true elongation.

What I claini is: 1

1. In an apparatus for testing. materials with regard to their tensile strength, in combination, stationary means for securely mounting one .end of a bar of the material' to be tested, movable device in a manner opposite tothat in which the indicator device is operated" by the first-mentioned test bar.

-2. In an apparatus for testing materials with regard to their tensile strength, in combination, stationary means for securely mounting one end 01' a bar or the material to be tested, movable means for securely mounting the other end of said test bar, a loading device connected with said movable means for stretching said test bar,

stretched, to the indicator device, means for holding a second barofthe material to be tested, said second bar being of the same length as the test bar and being placed adjacent the same so being adapted for securely mounting one of said bars and loosely mounting the other bar, a loading device in connection with the movable holder for stretching the bar securely mounted between the holders, an indicator device, for measuring the elongation of the securely mounted bar, means operatively connecting the securely mountedbar with said indicator device to act upon the latter in a certain direction, and means operatively connecting the loosely mounted bar with said indicator device to act upon the same in a direction opposite to that of the securely mounted bar.

4. In an apparatus Ior testing materials with regard-to theirtensile strength, in combiiiation, a stationary holder .and a movable holder Ior carrying betweenthem two substantially equal bars or the material to be tested, a loading device connected with the movable holder, each holder having a screw hole for securely mounting one of the bars, to be stretched by the loading device,

each holder also having a recess therein for loosely mountingthe other bar, the movable holder having two bores, which bores form extensions 01' said screw hole and recess/in this holder, a bar mounted slidably in each one of i said boresin contact with the corresponding bar slida'ble bars protrude, a lever one end of which means for securely mounting the other end or said test bar, a loading device connected with said movable means for stretching said 'tat bar, an indicator device connected to said test bar ior measuring, the elongations o! the, same, means for holding a second bar of the material to be.

tested, said second bar being or the same'length as the test bar and being placed adjacent the variations of the length of said second bar, caused is in contact with said slidable bar contacting the loosely mounted bar of the material to be tested, a stationary prop for supporting the other end of said lever, a second lever one end 01 which is in contact with .saidslidable bar contacting the securely mounted bar of the material to be tested, a fulcrum tor the last-mentioned lever which tulcrumcouples together said two levers at an intermediate point or such location that it divides each lever in two parts the'r'atio oithe parts or one lever beingas the ratio or the parts of the other lever; and an indicator device which is connected to that end or the last-mentloned lever which is not in contact with the j corresponding slidable for measuring the stretched by the loading device.

by changes or the temperature. to said indicator 76 5- An apparatus for testing materials with regard to their tensile strength, as claimed in claim 4, wherein said slidable bars connecting the bars of the material to be tested, with the levers acting upon the indicator device, consist of a material such as quartz.

6. In an apparatus for testing materials with regard to their tensile strength, in combination, stationary means for securely moun of a bar of the material to be tesl anovable means for securely mounting the other end of said test bar, a, loading device confiected with said movable means for stretching said test bar, Q

an indicator device connected to said test bar for one end measuring the elongations of the same, means for holding a second bar of the material to be tested, said second bar being of the same length as the test bar and being placed adjacent the same, means for transmitting the variations of the length of said second bar, caused by changes of the temperature, to said indicator device in a manner opposite to that in which the indicator device is operated by the first-mentioned test bar, and a heat-insulated chamber for enclosing said bars.

'7. In an apparatus for testing materials with regard to their tensile strength, in combination, stationary means for securely mounting one end of a bar of the material to be tested, movable means for securely mounting the other end of said test bar, a loading device connected with said movable means for stretching said test bar, an indicator device connected to said test bar for measuring the elongations of the same, means for holding a second bar of the material to be tested, said second bar being of the same length as the test bar and being placed adjacent the each holder also having a recess therein for securely mounting between the holders a bar of the material to be tested, each.holder also having a recess therein for loosely mounting between the holders a second bar of the material to be tested, said second bar being of the same length as the test bar, a loading device in connection with said movable holder for stretching only the securely mounted bar, and an indicator device operated in opposite directions by the bars when variations of .the length of the two bars occur due to temperature changes.

9. Inanapparatus for testing materials with regard to their tensile strength, in combination, a chamber formed with two opposite end walls and consisting of a heat-insulating material, a lining in this chamber consisting of a heat-proof mesame, means for transmitting the variations of the length of said second bar, caused by changes of the temperature, to said indicator device in a manner opposite to that in which the indicator device is operated by the first-mentioned test bar, a heat-insulated chamber for enclosing said --supporting said chamber, a stationary .holder connected with the stand and protruding through one of the end walls of the chamber into the space of they same, a movable holder slidably mounted in the opposite. end wall of the chamber and also protruding into thespace of the same,

te-rial, an electrical heating element in said chamber outside the heat-proof lining, a stand supporting said chamber, a stationary holder connected with the stand and protruding through one of the end Walls of the chamber into the space of the same, a movable holder slidably mounted in the opposite end wall of the chamber and also protruding intothe space of the same, a loading device connected with the movable holder, each holder having a screw hole for securely mounting a, bar of the material to be tested, to be stretched by the loading device, each holder also having a recess therein for loosely mounting a second bar of the material to be tested, the movable holder having two bores which bores form extensions of said screw hole and recess in this holder, a bar mounted slidably in each one of said bores in contact with the corresponding bar of the material to be tested, the movable holder also having a transverse aperture into which said slidable bars protrude, a lever one end of which is in contact with said slidable bar contacting the loosely mounted bar of the material to be tested, a stationary prop for supporting the other end of said lever, a second lever one end of which is in contact with said slid able bar contacting the securely mounted bar of the material to be tested, a fulcrum for the lastmentioned lever which fulcrum couples together said two levers at an intermediate point of such 

